1. Field of the Invention
The invention relates to an apparatus for the automatic performance of diagnostic and/or therapeutic actions in body cavities. Relevant instruments are catheters, cannulae, electrodes, endoscopes or the like, with body cavities meaning all kinds of organs and vessels to be examined in the human or animal body.
2. Background Art
A fundamental problem in these medical instruments resides in piloting them to the desired place of diagnosis or treatment within the cavity. Conventional mechanical steering devices are for instance rigid mandrels as a core or wire pulls in a catheter, it being possible, by a pull at these elements, to modify the twist and turn of the tip of a catheter, thus changing the direction of advance.
The prior art teaches various implements of the generic type, in which piezoelectric elements are used for control purposes. For example, U.S. Pat. No. 6,066,094 discloses a method and an apparatus of constructing a cardiac map of the heart, in which a steerable catheter is brought into contact with several locations in the heart where it is used to make measurements. U.S. Pat. No. 5,415,633 relates to an implantable instrument the distal end of which has sort of an annex that is controllable by means of piezoelectric elements.
U.S. Pat. No. 5,419,312 describes an endoscope coated with piezoelectric ceramic for controlling and steering purposes. This helps attain active pliability of the endoscope. A similar device is disclosed by U.S. Pat. No. 6,048,307. Finally, WO 97/22155 relates to a so-called piezoelectric motor working on the basis of an adjustable-length piezoelectric element.
It is an object of the invention to further develop a device of medical engineering of the type mentioned at the outset so that the actuator thereof is in a position largely automatically to move into contact with a single target or a plurality thereof, there taking corresponding diagnostic or therapeutic measures.
This object is attained by provision of a base control unit which is preferably extracorporal and with which is coupled an actuator of the type of a catheter that is insertable into the corresponding body cavity. In the vicinity of its distal end, the actuator is provided with a diagnostically active detection equipment or a therapeutically active treatment equipment, such as an ablation electrode, a dilatation balloon or the like. At least in the vicinity of its distal end and possibly over its full lengthxe2x80x94if necessary for reasons of maneuverabilityxe2x80x94the actuator is provided with an actuation mechanism for advance and/or twist and turn control that is triggered by the base control unit. Consequently, the base control unit may independently control the actuator and have him move into contact with certain locations, based on a corresponding control circuit or, in the way of a computerized numerical control system, based on a corresponding control program. Information about a surface contact of the distal end may be passed to the base control unit as input variables for the control system and may be used directly as a feedback variable in the control system. To this end, contact sensors are disposed preferably on the actuator""s distal end, detecting any mechanical contact with the wall of the body cavity.
In keeping with further preferred embodiments, measuring sensors may be disposed on the actuator""s distal end, detecting medically relevant data. These data may serve for diagnostic purposes, but they may also be used in the position control of the actuator. For instance, the instrument can localize pathological electric signals in the heart by measuring the potential on the myocardium. The instrument may spot locations that are to be treated by the actuator scanning the myocardium and by its measuring the corresponding potential signals.
Automatic placement in the vicinity of a stenosis is also conceivable to take place by means of impedance measurement in the vessel for the detection of blood stream and vessel volume.
Three-dimensional maps of coordinate plots of the cavity to be examined, which have been obtained by the aid of imaging techniques, may also serve as an alternative data base for the control of the actuator, in which case the respective location coordinates of the actuator are interrelated and corresponding control action is taken in accordance with the actuator""s xe2x80x9cschedulexe2x80x9d. Finally it also possible, alternatively or additionally, to place a so-called xe2x80x9cnavigation markxe2x80x9d as a point of reference in or in the proximity of the body cavity or even to arrange it extracorporally, this mark being detectable by corresponding sensors of the actuator. Based on this, signals may then be passed on to the base control unit, which are representative of the actuator""s current position relative to the navigation mark. As actual actuation elements for the actuation mechanism of the actuator, the piezoelectric elements already mentioned, but also electrostrictive polymer elements (so-called xe2x80x9cnanotubesxe2x80x9d) may be used as well as pneumatic or hydraulic actuation elements. Even the use of micro mechanic machine elements in nanotechnology is feasible, i.e. tiny gears, motors, transmissions etc.
Further preferred embodiments relate to special problems which occur distinctly during the application of the apparatus according to the invention in or on the heart. Being a pumping organ, the heart makes strong movements when it beats. Vessels next to the heart or the walls of the heart may easily collide comparatively vehemently with a catheter that has been inserted in the heart, which implies a certain risk of injury. Furthermore, keeping the precise position of treatment may be rather difficult or inaccurate because of the heartbeat. The consequences can be serious, in particular in the case of so-called ablationsxe2x80x94i.e. sclerosing myocardial tissue for the suppression of pathological arrhythmias.
To avoid these problems, provision can be made for the actuator to track the motions of the body cavity which have been detected by suitable measuring or contact sensors, with the base control unit performing a corresponding feed and/or twist and turn control of the actuator. Further features, details and advantages of the invention will become apparent from the ensuing description of exemplary embodiments of the subject matter of the invention, taken in conjunction with the drawing.